Departamento de Química, Facultad de Ciencias Exactas Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba, Argentina.
J Photochem Photobiol B. 2013 Aug 5;125:179-87. doi: 10.1016/j.jphotobiol.2013.06.007. Epub 2013 Jun 21.
Photoinactivation of Streptococcus mitis induced by zinc(II) 2,9,16,23-tetrakis[2-(N,N,N-trimethylamino)ethoxy]phthalocyanine (ZnEPc(4+)) was studied under different experimental condition in order to obtain information about the photodynamic processes and the cellular damage. A 3 log decrease in S. mitis survival was found in cell suspensions (~2×10(8) cells/mL) incubated with 2 μM ZnEPc(4+) and irradiated for 30 min with visible light (54 J/cm(2)). Also, S. mitis cells growth was not detected in broth treated with 5 μM ZnEPc(4+) under continuous irradiation. Studies of photodynamic action mechanism showed that the cells were protected in the presence of azide ion, while the addition of mannitol did not produce a significant effect on the survival. Moreover, the photocytotoxicity was increased in D2O indicating the interference of singlet molecular oxygen. On the other hand, it was found that ZnEPc(4+) interacts strongly with calf thymus DNA in solution but photocleavage of DNA was only detected after long irradiation periods. After S. mitis photoinactivation, modifications of genomic DNA were not observed by electrophoresis. In contrast, the transmission electron microscopy showed structural changes in the S. mitis cells, exhibiting mesosome-like structures. After 2h irradiation, the cytoplasm showed segregation patterns and PDI appeared to have effects on the cell wall, including variability in wall thickness. Also, the presence of bubbles was detected on the cell surface by scanning electron microscopy. However, the photodamage to the cell envelope was insufficient to cause the release of intracellular biopolymers. Therefore, modifications in the cytoplasmic biomolecules and alteration in the cell barriers could be mainly involved in S. mitis photoinactivation. It can be concluded that photosensitization by ZnEPc(4+) mainly involved a type II photoprocess, while alteration in the cytoplasmatic components and modifications in the cell envelope were the major cause for the photoinactivation of S. mitis.
锌(II)2,9,16,23-四[2-(N,N,N-三甲氨基)乙氧基]酞菁（ZnEPc(4+)）诱导变异链球菌的光灭活作用在不同实验条件下进行了研究，以便了解光动力学过程和细胞损伤。在细胞悬液（~2×10(8)个细胞/mL）中孵育 2 μM ZnEPc(4+)，并用可见光（54 J/cm(2)）辐照 30 分钟，发现变异链球菌的存活率下降了 3 个对数级。此外，在连续辐照下，用 5 μM ZnEPc(4+)处理的肉汤中未检测到变异链球菌的生长。光动力作用机制的研究表明，在叠氮化物离子存在下，细胞受到保护，而甘露醇的添加对存活率没有显著影响。此外，在 D2O 中，光细胞毒性增加，表明单线态氧的干扰。另一方面，发现 ZnEPc(4+)在溶液中与小牛胸腺 DNA 强烈相互作用，但仅在长时间辐照后才检测到 DNA 的光裂解。在变异链球菌光灭活后，电泳未观察到基因组 DNA 的修饰。相比之下，透射电子显微镜显示了变异链球菌细胞的结构变化，表现出类中介体结构。在 2 小时照射后，细胞质显示出分离模式，并且 PDI 似乎对细胞壁有影响，包括细胞壁厚度的变化。此外，扫描电子显微镜检测到细胞表面存在气泡。然而，细胞包膜的光损伤不足以导致细胞内生物聚合物的释放。因此，细胞质生物分子的修饰和细胞屏障的改变可能主要参与变异链球菌的光灭活。可以得出结论，ZnEPc(4+)的光敏化主要涉及 II 型光过程，而细胞质成分的改变和细胞包膜的修饰是变异链球菌光灭活的主要原因。
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